On my MK4, I noticed that the Silver getter flashing of my VR tubes (NOS RCA 0A3 and RCA 0C2) are steadily receding since day one. I've owned the MK4 for only about 2 months now.

Just wanted to clarify that I am concerned about the rate of disappearance rather than the disappearance itself.I understand that it is normal for the silver getter flashing to disappear progessively from tubes. But the rate seems to be faster for the OA3 and 0C2 tubes vs the other Power tubes, rectifiers and input preamp tubes.

With 950 hours on my MKIII/MK IV conversion, the OC2's look the same as when they were new.

On my early 50's RCA OA3's, the getters and silver flashing inside the glass, look the same as the TungSol 5U4G's I am running. The getters have not shrunk in size from what I can see, but the amount of silver flashing inside the glass has increased somewhat.

It takes many, many, hours before 7308's change visually. At least for me.